This invention relates to the field of biochemistry, and more particularly relates to animal feed compositions.
Phytate Phosphorus Utilization
Animals, including humans, require phosphorus in their diets for proper growth and health. Farm animals are normally fed a grain-based animal feed. Most of these grain-based feeds contain from 50-80% of their total phosphorus as phytate phosphorus. Phytate phosphorus in plants occurs as the mixed calcium-magnesium-potassium salt of the organic compound, phytic acid.
Many animals are unable to utilize most of the phytate phosphorus they receive in their feed. For example, studies by Edwards and Veltmann, J. Nutr. 113:1268-1575 (1983) and Ballam et al., Poultry Sci. 63:333-338 (1984) with young broiler chickens fed corn-soybean diets indicate phytate phosphorus utilization of from only 10 to 53%. Feed consumed by these animals must be supplemented with inorganic phosphorus, such as in the form of dicalcium phosphate or defluorinated phosphate. The cost of phosphorus supplementation is high. In addition, the unused phytate phosphorus is excreted, creating phosphorus soil contamination and costly ecological problems.
The mechanisms involved in phytate phosphorus utilization by animals are unknown. Utilization of phytate phosphorus by chickens has been reviewed by several scientists including T. S. Nelson, Poultry Sci. 46:862-871 (1967). Phytate phosphorus utilization in broiler chickens has been shown by Edwards et al., Poultry Sci. 67:1436-1446 (1988) to be influenced by age. Other scientists, such as Lowe and Steenbock, Biochem J. 30:1992-1995 (1936), Common, Agric. Sci. 30:113-131 (1940), Edwards and Veltmann, J. Nutr. 113:1268-1575 (1983), Ballam et al., Poultry Sci. 63:333-338 (1984) and Sooncharernying and Edwards, Poultry Sci. 69(Suppl. 1):129 (1990), have shown that phytate phosphorus utilization may be influenced by calcium, phosphorus, and aluminum levels in the diet.
A method that would increase phytate phosphorus utilization by animals, especially farm animals such as chickens, would reduce the costs of raising such animals because phosphate supplementation would be unnecessary. In addition, the soaring costs associated with the decontamination of soil containing elevated phosphates would be greatly reduced or even eliminated.
Tibial Dyschondroplasia
Tibial dyschondroplasia is a skeletal abnormality which occurs in rapidly growing animals such as broiler chickens or turkeys. The cause of tibial dyschondroplasia is unknown. Tibial dyschondroplasia is distinguished from rickets, a vitamin D deficiency disease characterized by overproduction and deficient calcification of osteoid tissue, in that a high incidence of tibial dyschondroplasia is found in animals that receive a sufficient dietary supply of vitamin D and are adequately exposed to sunlight.
Tibial dyschondroplasia is characterized by an unmineralized, unvascularized mass of cartilage located in the proximal ends of the tibiotarsus and the tarsusmetatarsus. The cartilage extends from the growth plate into the metaphysis. In fowl, tibial dyschondroplasia usually appears between three and eight weeks of age. In some chickens and turkeys, the prehypertrophic cartilage persists into adulthood but is restricted to the posterior medial portion of the proximal tibiotarsal bone so that the birds remain clinically normal. An incidence of 10 to 30% of birds with subclinical dyschondroplasia is common in many flocks. In the more severe cases of tibial dyschondroplasia, the abnormal tissue occupies the whole metaphysis of the proximal tibiotarsal bone and also develops in the proximal tarsometatarsal bone.
Birds with these more severe lesions may be lame, with bowing of the affected bones. These chickens are unable to walk normally and often collapse, causing injury and decreasing growth rate. The disease also increases the death rate of animals during the growth period. Further, many of the birds suffering from tibial dyschondroplasia develop breast blisters and leg deformities that result in hemorrhages.
Tibial dyschondroplasia increases the percentage of carcasses that must be downgraded or condemned during processing, resulting in decreased profits for the processor. The deformed legs of birds with tibial dyschondroplasia often interfere with the shackling of the fowl during processing and can actually cause mechanical problems in operating the processing line where the slaughtered fowl are conveyed on machines which handle the birds by their legs. Fowl with tibial dyschondroplasia have insufficient leg strength to be carried in this manner.
A number of studies have been conducted to determine both the cause of dyschondroplasia and a method for treatment or prevention. Leach and Nesheim, "Further Studies on Tibial Dyschondroplasia Cartilage Abnormality in Young Chicks",J. Nutr. 102:1673 (1972), indicated that the cartilage abnormality is a result of an inherited physiological defect, the expression of which is under dietary control. They were not able to determine the nutritional factors responsible for expression. However, they found that manipulations of the mineral mixture that resulted in changes in acid/base or cation/anion balance in the chick altered the incidence of abnormality. In particular, high chloride level in the diet increased the incidence of the abnormality.
Mongin and Sauveur, in "Interrelationship Between Mineral Nutrition, Acid-Based Balance, Growth and Cartilage Abnormalities," Growth and Poultry Meat Production, Borman, K. N. and Wilson, B. J., Eds., pp. 235-247, British Poultry Science Ltd., Edinburgh, Scotland (1977), hypothesized that the metabolic acidosis in chickens fed high dietary chloride levels caused tibial dyschondroplasia because of impaired bone mineralization resulting from alteration of vitamin D metabolism.
In most animals, including humans, vitamin D.sub.3 (cholecalciferol) is metabolized first by hydroxylation at the C.sub.25 position to 25-hydroxycalciferol by one or more enzymes present in the liver, and then hydroxylation of the 25-hydroxycalciferol at the C.sub.1 position to calcitriol (1,25-dihydroxycholecalciferol) by one or more enzymes present in the kidneys. A flow chart showing the chemical structures involved in vitamin D derivation and metabolism is shown in FIG. 1.
Chickens made acidotic by administration of ammonium chloride show reduced conversion of 25(OH)D.sub.3 to 1,25(OH).sub.2 D.sub.3, although the production of 24,25-dihydroxycholecalciferol (24,25(OH).sub.2 D.sub.3) from 25(OH)D.sub.3 is not consistently affected by acidosis as also reported by Sauveur and Mongin in "Influence of Dietary Level of Chloride, Sodium and Potassium on Chick Cartilage Abnormalities," Proceedings of XV World Poultry Congress, pp. 180-181 (1977).
However, supplementation of chickens with 20 ng/day of either 1,25-dihydroxycholecalciferol (1,25(OH).sub.2 D.sub.3) or 24,25-dihydroxycholecalciferol (24,25(OH).sub.2 D.sub.3) has been demonstrated to have no effect on the incidence of tibial dyschondroplasia, as described by Edwards in "Studies on the Etiology of Tibial Dyschondroplasia in Chickens", J. Nutr., 114:1001 (1984).
Calcium and phosphorus levels in the diet have been found to be major nutritional factors influencing the expression of tibial dyschondroplasia. High calcium in the feed retards development of the lesion, whereas high phosphorus levels appear to accentuate the development of the lesions, as reported by Edwards and Veltmann, "The Role of Calcium and Phosphorus in the Etiology of Tibial Dyschondroplasia in Young Chicks, " J. Nutr., 13:1568 (1983).
Increases in the magnesium content of the chick diet decrease the incidence of tibial dyschondroplasia; however, the effect of magnesium is not as strong as that of calcium,, as demonstrated by Edwards, "Studies on the Etiology of Tibial Dyschondroplasia in Chickens" J. Nutr., 114:1001 (1984).
Given the large economic loss to meat producers caused by animals afflicted with tibial dyschondroplasia as well as the discomfort of the afflicted animal and the resulting unsanitary conditions caused by the diseased dysfunctional animal, it would be of great benefit to find an effective method and compositions to reduce the incidence of this disease.
U.S. patent application Ser. No. 07/630,748, filed December 20, 1990, now U.S. Pat. No. 5,154,925 of which this is a continuation-in-part, discloses a method for treating tibial dyschondroplasia in fowl and other animals by administering to the animals a vitamin D.sub.3 derivative including 1,25-dihydroxycholecalciferol; 1,25-dihydroxy-26,27-hexadeuterocholecalciferol; 1-hydroxycholecalciferol; 1,24,25-trihydroxycholecalciferol; 1,25-dihydroxy-24-fluorocholecalciferol; 25-hydroxycholecalciferol or combinations thereof. The derivative is administered or fed to animals in a pharmaceutical carrier including animal feed in a concentration between 0.10 and 20 micrograms of a vitamin D.sub.3 derivative per kilogram of body weight per day. U.S. Ser. No. 07/630,748 U.S. Pat. No. 5,154,925 will issue with claims directed to administration of the vitamin D.sub.3 derivatives 1,25-dihydroxy-26,27-hexadeuterocholecalciferol; 1,24,25-trihydroxycholecalciferol; and 1,25-dihydroxy-24-fluorocholecalciferol to fowl and other animals in a pharmaceutically acceptable carrier including animal feed.
It is therefore an object of the present invention to provide additional methods and compositions for the treatment and prevention of tibial dyschondroplasia in animals.
It is a further object of the present invention to provide methods and compositions for enhancing phytate phosphorus utilization in animals.
It is a further object of the present invention to provide a method and compositions for enhancing phytate phosphorus utilization while preventing or treating tibial dyschondroplasia.
It is a further object of the present invention to provide methods and compositions for decreasing phosphorus contamination of soil by animals.
It is a further object of the present invention to provide economical animal feed compositions containing reduced levels of supplemental calcium and phosphorus.